1. Field of the Invention
This invention relates to a motion detector unit for detecting a moving person or object by means of doppler frequency shift.
2. Description of Related Art
The use of the doppler effect for detecting such motion is well-known. Typical applications include intruder alarms and automatic door openers, for which a unit of conventional construction comprises a gunn diode oscillator mounted in a cavity resonator such as a simple waveguide tube. A diode mixer also mounted in the tube provides an output at the doppler frequency. This construction has a number of drawbacks: its relative complexity for mass-production, the power consumption of the oscillator, and, especially, difficulties in meeting the stringent harmonic radiation suppression requirements imposed by the regulatory authorities in most countries.